Making Change [spur] Gears

A 45 tooth 1.0 m/m module change gear made by the students to increase the number of
threads possible to produce on the Emco Compact 10 lathes.

Specifications:

specifications

1.00 m/m module

25.4 diametrical pitch

number of teeth

45

45

over all diameter

47.00 m/m

1.850 inches

gear face width

9.00 m/m

0.357 inches

width over hub

10.00 m/m

0.391 inches

bore diameter

19.00 m/m

0.748 inches

key slot width

4.00 m/m

0.157 inches

bottom of key slot to opp.side

21.00 m/m

0.821 inches

The 45 indicates the number of teeth. K is for Keith Morris, T is for Troy
Stephens, and P is for Paul Hammack, the student machinists who manufactured this gear.

An air powered die grinder was used to shape the fly cutter tool to the proper involute
shape when checked with another gear. The indexing of the teeth was done using a
rotary table with 10' venier angular measurement. The rotary table was
upgraded after the production of this gear by the addition of the index plates required to
convert it into a dividing head.

A #2 MT arbor to mount the gear blank to the rotary table was produced using a 3/4 inch
fine thread bolt. The diameter of the bolt's threads was almost exactly 19
m/m. Both ends of the bolt were center-drilled while being held in a collet to
insure concentricity. The bolt was then held between centers while a truing cut
removed a few thousandths from the crests of the threads. The tailstock was then set
over to produce the required #2 MT taper. The end of the taper was drilled and
tapped for a retaining bolt in the rotary table because of the interrupted cut of the
fly-cutter forming tool.

Manufacture of this gear not only increased the capability of our existing machines,
but gave the student machinists hands-on experience with die- grinding to a template or
gage, center drilling, turning between centers, taper turning, angular measurement, use of
a boring head, reverse engineering, metric gear nomenclature, and cutting an operational
gear.

The material required for the production of the remaining change gears is on hand, and
this remains an ongoing project.

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last updated by GmcD on 19-Mar-11 19:30
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